Nucleic acids will be sequenced and nucleic acid sequences will be analyzed for constraints on nucleotide order that may be a consequence of Genotypic Selection. Genotypic Selection is a novel form of selection postulated to exist at the intracellular level and acting directly on the nucleic acids before their expression. The constraints imposed on actual nucleotide sequences will be examined for patterns of internal terminator sequences, true palindromic sequences, self-complementary sequences, and frequencies of 2-8 long nucleotide groups and their contexts. These patterns will also be analyzed for their relationship to each other. For example, the gene V ribosome binding site of f1 bacteriophage sequence, AUG.AUU.AAA.GUU.GAA.AUU.AAPu, is composed of internal terminators palindromically arranged. In addition the nature of tRNA-mRNA interaction will be examined at the nucleotide level to determine the actual number of base pairs required per interaction. The allowable conformations for tRNA anti-codon loops can then be determined as well as the question of messenger RNA species specificity. A model of tRNA interaction has recently been proposed by Crick, Klug, Brenner, and myself. I have found by computer analysis of certain known sets of tRNA and mRNA sequences, particular ones which are uniquely suited for testing this hypothesis. I have demonstrated tRNA-tRNA complexes that are dimers, trimers, tetramers and pentamers of a given tRNA. These multimers will be isolated and characterized by nucleotide blocking and nuclease digestion. Complexes of tRNA-mRNA will be generated and analyzed for the nature of the tRNA-mRNA interaction. Also, the direct sequencing of certain DNA restriction fragments of phi80 and f1 bacteriophages and the indirect sequencing of adjacent regions will be done to determine transcription starts, attenuators and stop sequences as well as additional coding sequences. The significance of such studies is that they allow a test of the predictions of Genotypic Selection; a perspective where the genotype is a phenotype for syntactical and structural selection by the replication, transcriptional and translational machinery.